Correction of Depth Bias in Upper-Ocean Temperature and Salinity Profiling Measurements from Airborne Expendable Probes

Denny P. Alappattu Department of Meteorology, Naval Postgraduate School, Monterey, California

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Qing Wang Department of Meteorology, Naval Postgraduate School, Monterey, California

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Abstract

During the Dynamics of Madden–Julian Oscillation (DYNAMO) Experiment in 2011, airborne expendable conductivity–temperature–depth (AXCTD) probes and airborne expendable bathythermographs (AXBTs) were deployed using NOAA’s WP-3D Orion aircraft over the southern tropical Indian Ocean. From initial analysis of the AXCTD data, about 95% of profiles exhibit double mixed layer structures. The presence of a mixed layer from some of these profiles were erroneous and were introduced because of the AXCTD processing software not being able to correctly identify the starting point of the probe descent. This work reveals the impact of these errors in data processing and presents an objective method to remove such erroneous data from the profiles using spectrograms from raw audio files. Reconstructed AXCTD/AXBT profiles are compared with collocated shipborne conductivity–temperature–depth (CTD) and expendable bathythermograph (XBT) profiles and are found to be in good agreement.

Corresponding author address: Denny P. Alappattu, Department of Meteorology, Naval Postgraduate School, 589 Dyer Road, Root Hall, Monterey, CA 93943-5114. E-mail: dpalappa@nps.edu

This article is included in the DYNAMO/CINDY/AMIE/LASP: Processes, Dynamics, and Prediction of MJO Initiation special collection.

Abstract

During the Dynamics of Madden–Julian Oscillation (DYNAMO) Experiment in 2011, airborne expendable conductivity–temperature–depth (AXCTD) probes and airborne expendable bathythermographs (AXBTs) were deployed using NOAA’s WP-3D Orion aircraft over the southern tropical Indian Ocean. From initial analysis of the AXCTD data, about 95% of profiles exhibit double mixed layer structures. The presence of a mixed layer from some of these profiles were erroneous and were introduced because of the AXCTD processing software not being able to correctly identify the starting point of the probe descent. This work reveals the impact of these errors in data processing and presents an objective method to remove such erroneous data from the profiles using spectrograms from raw audio files. Reconstructed AXCTD/AXBT profiles are compared with collocated shipborne conductivity–temperature–depth (CTD) and expendable bathythermograph (XBT) profiles and are found to be in good agreement.

Corresponding author address: Denny P. Alappattu, Department of Meteorology, Naval Postgraduate School, 589 Dyer Road, Root Hall, Monterey, CA 93943-5114. E-mail: dpalappa@nps.edu

This article is included in the DYNAMO/CINDY/AMIE/LASP: Processes, Dynamics, and Prediction of MJO Initiation special collection.

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